Version 1.6.4 of the Arduino IDE introduced official support for adding third party boards (like the Adafruit Flora and Trinket) to the new Board Manager. This addition is great news, because it allows users to quickly add new boards with the click of a button. Previously the addition of new boards required a cumbersome manual installation process, or in certain cases, the download of a completely separate version of the IDE with the new boards added.
The new Board Manager solves those issues. We had figured out a way to add custom boards in v1.6.3 of the Arduino IDE, but it was not officially supported by Arduino. Thanks to the hard work of Federico Fissore and the Arduino developer community, we can now add new boards just as easily using officially supported methods. Let's get started.